Vertex snapping with edge slide?
A solution is:  


Select the edge you want your vertex to slide and press Shift+NumPad7 to snap view to selected;
Then press Ctrl+Alt+Spacebar to create new transform orientation;  
Choose it from available transform orientations in the 3d Viewport header (or press Alt+Space) Optionally give it a meaningful name chck USE VIEW;  
Move the vertex with G using the new transform orientation instead of Local or Global etc. Snap will work as usual.